This invention relates to printing presses in general and, in particular, to a rotary printing press providing for a change of printing plates without a pause in printing.
The concept of a printing press capable of nonstop operation during a change of printing plates is itself not new. Japanese Utility Model Publication No. 3-47886 and Japanese Patent No. 2,589,863 are hereby cited as teaching printing presses constructed toward that end. These prior art machines are alike in having two plate cylinders independently movable into and out of printing engagement with an impression cylinder, either directly or via a blanket cylinder. When either plate cylinder is in printing engagement with the impression, or blanket, cylinder, the other plate cylinder is held away therefrom and declutched from the power transmission system of the press for a change from one printing plate to another. Upon mounting of a new printing plate, the plate cylinder is driven at a peripheral speed matching the printing speed and moved back into printing contact with the impression, or blanket, cylinder, from which the plate cylinder that has so far been in use is moved away.
Despite the compactness of the cylinder configuration according to the noted prior art machines, they do, however, possess some shortcomings that are in urgent need of rectification. First, in these prior art machines, the rotational speed of the impression cylinder is the norm in reference to which the rotations of the plate cylinders and blanket cylinder are controlled. The plate cylinders required clutches and speed control means of very complex constructions as they were individually moved into and out of printing engagement with the impression cylinder.
According to Japanese Patent No. 2,589,863, supra, in particular, a plurality of plate cylinders are arranged at circumferential spacings around one impression, or blanket, cylinder for making as many different printings at the same time, thereby providing for a change in shop name or the like within one printing unit. This construction almost made it impossible to make interchangeable use of different diameter sets of plate cylinders and blanket cylinders.
The rotary printing press constructed for interchangeable use of different size cylinders has itself been known. When this type of press is constituted of a series of printing units of identical make, the driving of the impression cylinders of all the printing units from one common drive shaft for synchronization purposes is undesirable, because then the plate cylinders and blanket cylinders have to be driven separately at the cost of very complex and duplicate means.
An aim of the present invention is the provision of a rotary printing press that permits a nonstop printing during a change of printing plates with use of simple drive and speed control means.
Another object of the invention is to adapt the printing press, having the capability set forth above, for interchangeable use of different diameter sets of cylinders.
Briefly, the invention provides a rotary printing press capable of nonstop printing during a change of printing plates, which comprises a series of printing units through which a web of paper or the like is to be threaded one after another in order to be printed. Each printing unit comprises in its simplest form a plate cylinder and an impression cylinder, the plate cylinder being movable into and out of printing engagement with the impression cylinder. Also provided for each printing unit, a drive motor is coupled by a drive linkage to the plate cylinder and thence, via a clutch, to the impression cylinder regardless of whether the plate cylinder is in or out of printing engagement with the impression cylinder.
Such being the construction of the two or more printing units constituting the printing press according to the invention, a plate change is possible in any of the printing unit while the other printing unit or units print the web. Any desired printing unit can be conditioned for a plate change merely as the plate cylinder is moved out of printing engagement with the impression cylinder, and the impression cylinder declutched from the drive linkage. During the subsequent progress of a plate change, the impression cylinder stays in the same position as when printing was being made in this printing unit. Furthermore, being declutched from the drive linkage, the impression cylinder is free to rotate in frictional contact with the web, holding the same under the same tension as before and so enabling the other printing unit or units to print the web without a hitch.
The printing units according to the invention are each much simpler in construction than the prior art machine in which a plurality of plate cylinders are selectively moved into and out of printing engagement with the impression cylinder or with the blanket cylinder. Each printing unit is made even simpler by the provision of a dedicated drive motor and dedicated drive linkage for the cylinders.
In the preferred embodiment of the invention to be disclosed herein, each printing unit takes the form of an offset press, itself well known in the art, comprising a plate cylinder, a blanket cylinder and an impression cylinder. The blanket cylinder is made movable into and out of printing engagement with the plate cylinder and the impression cylinder in this application of the invention. The impression cylinder occupies the same position during a plate change as during printing and, declutched from the drive linkage, serves as a tension roller for the web as the latter is printed in the other printing unit or units.
The above and other objects, features and advantages of this invention will become more apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing the preferred embodiment of the invention.